Revealing mistake: Near the end of the movie when everyone except for Peter dies. Lucy is supposed to be dead, but we can still see her breathing.
Revealing mistake: When Jack Swallows stabs Edward with the knife he is injured and passes out, there is no blood on the knife and there is no mark on his shirt.
Revealing mistake: When Susan is chugging beer, it's quite obvious there's nothing in the hose.
Revealing mistake: At the end of the movie when everyone is fighting the White Bitch, and Peter runs across 4 men and slices them open with the sword, you can see the first guy in the line falls a little too early.
Chosen answer: This is nothing more than a lame "breaking the fourth wall" gag. Basically, by making the expression the dwarf is showing that all of the actors are just standing still, as opposed to being really frozen.
Manky